The present invention relates to an annular combustion chamber for a gas turbine engine, such as a turbojet aircraft engine, more particularly such a combustion chamber having variable oxidizer intakes.
Generally annular combustion chambers for gas turbine engines are known which have fuel injectors associated with oxidizer swirlers located in an upstream end of the combustion chamber in order to inject fuel and oxidizer into the combustion chamber burning zone. The oxidizer swirlers impart a swirling motion to the incoming oxidizer in order to increase its mixing with the injected fuel. The oxidizer swirlers may be equipped with control diaphragms to control the cross sectional areas of the oxidizer swirler opening in order to control the amount of oxidizer passing into the combustion chamber.
Such known oxidizer swirlers with control diaphragms find particular use in aircraft turbojet engines which must experience extremely different modes of operation. At low engine power, a long dwell time of the combustion gases in the combustion zone are required to stabilize combustion, and to reduce the emission of carbon monoxide and unburnt hydrocarbons. On the contrary, under full power operating modes, the dwell time of the combustion gases in the combustion chamber must be relatively short in order to reduce nitrogen oxide emissions.
Known controllable oxidizer swirlers generate a large pressure drop in the oxidizer as it passes through the swirler into the combustion chamber. This causes a pressure buildup upstream of the oxidizer swirler which may overload the oxidizer compressor, which is utilized to supply the oxidizer to the combustion chamber. This consequently lowers the engine efficiency.